1. Field of the Invention
The present invention relates to furnaces for heating homes, commercial and public buildings and more particularly to a fuel saving structure for incorporation into existing as well as new furnaces to capture and utilize heat which would otherwise normally be lost through the flue and stack pipe and hence up the chimney.
2. Prior Art
The shortages and increasing costs of both oil and gas as fuels used in furnaces for heating homes, commercial and public buildings make it increasingly important that such furnaces make maximum utilization of the heat generated by such fuels in the furnaces. Conventional furnaces for hot air, hot water, or steam heating or buildings such as homes and the like, particularly hot air furnaces, usually have a substantial amount of space above the refractory material which forms the combustion chamber. The walls about this space are of metal and the heat and other products of combustion, in passing through this space to the flue, heat the space walls which form a heat exchanger for heating the air or other fluid medium on the other side of these space walls. Such heated fluid medium, usually air, water or steam, is in turn used to heat the building. However, much of the heat from the heating flame in the combustion chamber passes with the other products of combustion through this space above the combustion chamber to the flue opening and is lost through the stack and up the chimney.
The present invention incorporates in this open space a structure for absorbing and storing much of this normally lost heat during the "ON" periods of the heating flame in the combustion chamber and for this absorbed heat to thereafter continue to provide furnace heat during the "OFF" periods of the heating flame in the combustion chamber. The result is a greater utilization of heat generated by the fuel in the combustion chamber and thus a substantial saving in fuel.
While there are some existing structures which have been devised with heat absorbing material to store heat and subsequently discharge such stored heat for a particular purpose, such structures have generally required increased rather than decreased amounts of fuel than would be required if operated without the heat absorbing materials, and fail to recognize applicability for saving fuel in conventional furnaces for heating homes, commercial and public buildings. For example, U.S. Pat. Nos. 2,565,676 and 3,110,797 disclose stove structures for heating stones which are subsequently sprayed with water to generate steam for a steam bathroom. And stones are used with water in U.S. Pat. No. 3,369,541 to store heat from solar heat collectors to help in keeping the stored water warm. In U.S. Pat. No. 3,301,251 electric heating elements heat large slabs of concrete for subsequent use in an air conditioning system. Also, in U.S. Pat. Nos. 2,776,825, 2,890,876 and 3,493,344 a category of special purpose furnaces known a "pebble furnaces" for heat exchanger application in chemical processes use pebbles up to about one inch in diameter generally where temperatures are too high and conditions too severe for even the best alloy steels. Such pebble furnaces work on a relatively complicated timing movement of pebbles not reasonably applicable to the problem of saving fuel in conventional furnaces used in heating buildings such as homes and the like.
The present invention as will hereinafter become apparent provides a relatively simple and inexpensive solution to the problem of saving fuel in furnaces for heating homes, commercial and public buildings. The invention does not require close tolerance work nor the use of expensive materials and is applicable to any such furnace which has a substantial amount of space above the combustion chamber and "ON" and "OFF" periods of the heating flame in the combustion chamber, regardless of whether the furnace is for hot air, hot water or steam heating of the building. The invention is particularly applicable to gas and to oil fired furnaces.